Arata Ichikawa

Modeling for estimating representative water conditions in a river basin

Abstract The actual mechanism on the generation of pollution loading is so complicated that it should be simplified in modeling for its quantifications. Therefore, there is no perfect modeling for those. On the proposal of our new concept for modeling, we tried to describe the real phenomenon or mechanism from source to river more precisely. We have estimated generated pollution loading at a dry period per branch or drain in the middle basin of the Tama River. The data or materials for this investigation are based on the administrative informations which were summed up in 1981. In order to ascertain the calculated pollution loadings, these data were compared with the real water conditions which have been provided by the large-scale and simultaneous river survey in August 1981. We proposed the methodology for adjustment of observed values by ones from plural sections and described the real water conditions in the river. According to the ratio of estimated value and actual condition, we ascertained that our procedure or methodology of calculations for quantification of the generated pollution loadings is reasonable.

Japan's sewerage system

This paper traces the history of sewer construction in Japan. The first sewers were built for flood control, and as late as the end of the Second World War there were only six cities enjoying sewer systems with treatment facilities. Rapid industrialization increased pollution problems and led to accelerated sewer development. Advances in the technology of sewage treatment are outlined. Today 30% of Japans population is served by sewer systems, and identifying cost‐effective means of increasing that proportion is a major priority. The Experimental Sewer System, developed in Tokyo, is described. Finally, a new method for the estimation of peak flow in sewer pipes, entitled grid analysis, is presented.